Method of making white lead.



UNITED STATES PATENT onnron.

ALEXANDER S. RAMAGE, OF BUFFALO, NEW YORK, ASSIGNOR TO THE CHEMICALDEVELOPMENT COMPANY, OF BUFFALO, NEW YORK, A CORPORATION OF GOLD-Patented May 26, 1914.

Reno. v

METHOD OF MAKING WHITE LEAD.

1,097,672. Specification of Letters Patent.

No Drawing.

Application filed September 12, 1913. Serial No. ?89,532.

To all whom it may concern Be it known that I, ALEXANDER S. Item- AGE, acitizen of the United States, residing at Buffalo, in the county of Erieand State of New York, have invented certain new and useful Improvementsin, Methods of Making White Lead, of which the following is aspecification.

It has been proposed heretofore (U. S. Patent No. 431,505, issued July1, 1890, to Paul Bronner) to prepare white lead from normal lead sulfateby decomposing three equivalents of lead sulfate with two equivalents ofcaustic soda, forming thereby a basic sulfate of lead, and finallytransforming this basic sulfate into basic carbonate by reaction withsodium carbonate, using a small excess of soda beyond the quantity foundby calculation. I have found however that the quantity of sodiumcarbonate necessary to complete this decomposition is practically doublethe equivalent, or double the quantity found by calculation; and if thisamount were used without provision for its recovery the cost would beprohibitive. I have however found that by performing the reaction in theinverse direction, the same result as regards the preparation of basiccarbonate of lead may be obtained without loss of reagents. By usingapproximately two equivalents of sodium carbonate to three equivalentsof normal sulfate of lead, the mass reaction of the lead sulfate issuflicient to determine the complete conversion of the sodium carbonate,and I obtain a product as per the equation I then treat this product,which corresponds approximately to the formulaand may be regarded eitheras a more or less definite compound or as a-mixture of a carbonate andsulfate of lead, with two equivalents of caustic soda as per thefollowing equation:

The reaction is complete and the product is found to possess the properphysical properties of a basic carbonate of lead suited for use as apigment.

In. practice, I may place 909 pounds of pure white sulfate of lead in atank, and add thereto a solution of sodium carbonate containing 212pounds of the carbonate.

and that the solution contains only sodium sulfate.

I prefer to use a sodium carbonate solution of about fifteen per cent.concentration, and a caustic soda solution not above three per cent.concentration. The precipitate is allowed to settle and the clearsolution of sodium'sulfate is run ofi,-and the sodium sulfate recoveredin any of the known ways. The precipitated white lead is thoroughlywashed with water which has been.- previously purified by treatment witha basic lead compound, the washing being continued until the filtrateshows no trace of sodium sulfate.

It should be understood that the proportions above mentioned may beconsiderably varied. An excess of caustic soda may be used withoutaffecting the shade of the pigment, a matter of great importance whenlarge quantities of materials are handled by the ordinary workman. Inthe method of Bronner above referred to, on the contrary, for theconversion of all of the sulfate into 10 any slight excess of causticsoda immediately imparts a yellow shade to the basic sulfate, due to theformation of litharge.

I claim The method of preparing basic carbonate of lead from leadsulfate, which consists in reacting upon lead sulfate with an alkalicarbonate in less proportion than is required carbonate, and treatingthe resulting product with an alkali hydroxid.

In testimony whereof I affix my signature in presence of two witnesses.

, ALEXANDER S. RAMAGE. Witnesses v Wrnrnnn H. COOLING, FABWEIL LA TOUR.

